Final answer:
The question discusses biological immune response in the context of antibody levels post-vaccination, specifically asking for a decrease in levels after a year. The 'Effective dose - 50%' is then defined as the dose resulting in a significant response in 50% of subjects (ED50).
Step-by-step explanation:
The question on antibody (Ab) levels after vaccination probes the biological subject of immune response and vaccine efficacy, which would fall under high school Biology. While no concrete generic value can be provided, as antibody levels after vaccination can vary significantly depending on various factors such as the type of vaccine, the organism, and individual patient responses, the possible choices suggest it is a conceptual question aimed at understanding typical trends in antibody levels post-vaccination.
In the second part of the question related to 'Effective dose - 50%' within the context of pharmacology, the correct answer is D. The dose that results in a significant response in 50% of subjects. It is commonly referred to as ED50 (Effective Dose 50%), a term used in pharmacology to denote the dose of a drug that produces a therapeutic effect in 50% of the population taking it. This measure is often used to compare the potencies of different medications.